Europe's biggest ever Earth-observation satellite, Envisat, will go into orbit in the early hours of Friday (GMT). Project manager Derek Todman details the final preparations in Kourou, French Guiana, in his diary for BBC News Online.

Wednesday 27th February

One day to go!

This morning the launcher moved from the final assembly building to the launch pad.

The satellite has to be kept cool as it sits on the Ariane 5 rocket.

The total mass of the launcher is about 1,500 tons. The launch table runs on railway lines and is pulled by a small lorry about the size of those used at airports.

From the pictures you will notice a number of trailers. These are all the air conditioning units, which are used to keep the satellite cool while it is on the launch pad.

Babysitting job

The temperature here at the moment is about 30 degrees Celsius, so you can imagine how hot it would get under the fairing otherwise.

We now look forward to getting the first scientific data back from the instruments

At the moment, we are going through all the satellite preparatory activities such as loading the flight software. We allow ourselves plenty of time just in case we get a problem loading.

I will not be doing a diary tomorrow, so let me give you some idea of what is going to happen from now on.

Overnight we will babysit the satellite and during the day gradually get the satellite into its final configuration for launch.

Sitting and waiting

This includes the synchronisation of the onboard clock with the ground station clock and configuring the propulsion subsystem; basically opening a few valves between the tanks and thrusters.

Then as we approach launch, we switch from external power to internal power (batteries) about 10 minutes before launch.

Then sit and wait until we separate from the launcher.

The launcher people will tomorrow load the rocket with about 25 tons of liquid hydrogen and about 120 tons of liquid oxygen. Then, gradually, they will configure the rocket for launch and then lift off.

I hope you have all enjoyed the diary. I would like to thank the BBC for allowing us to share the last few weeks with you. Also thanks Sacha and Martyn for the photos.

We now look forward to getting the first scientific data back from the instruments.

Envisat will ride into orbit on an Ariane 5 rocket from Europe's spaceport in Kourou at 22:07 local time (02:07 CET, 01:07 GMT).

Built by a consortium of 50 companies led by Astrium, Envisat is the successor to the European Space Agency's ERS satellites. Envisat has an array of 10 instruments that will allow scientists to monitor the land, oceans, atmosphere and ice caps, to check on the health of the planet.